Prior efforts to create coatings having such properties have focused upon the use of biologically compatible coatings that are grafted onto the surface of an apparatus. Such polymers include polyacrylamide and poly(ethylene glycol). Polyacrylamide has been grafted onto substrates using photoinduced polymerization, while poly(ethylene glycol) has been chemisorbed onto gold surfaces, centrifugally cast from a polymer mixture into vascular conduits, and gamma-irradiated onto silane-treated glass, among other methods.
Some methods of treating apparatus with biologically compatible coatings are disclosed in U.S. Pat. Nos. 4,722,906; 4,973,493; 4,979,959; 5,002,582; 5,091,205; 5,217,492; 5,258,041; 5,263,992; and 5,414,075.
These prior methods for treating such apparatus to provide biologically compatible coatings have several demonstrated problems. First, the polymers fail to adhere to the substrate with enough strength or resistance to wear. The polymers also may not exhibit consistent molecular structure. The density of the biocompatible polymer on the surface of the apparatus also may be insufficient to provide the desired resistance to cell adhesion or protein adsorption. Indeed, the art has been unable to achieve both sufficient chain density and poly(ethylene glycol) polymer chain length to create a coating having the desired level of resistance to cell and bacterial adhesion and/or protein adsorption for extended periods of time in challenging environments.